"The main objective of this thesis is to study nonlinear dynamic of complex system with parametric modulation. As example of complex system, we choose Duffing oscillator and a fiber laser. Both the Duffing oscillator and laser equations model non-autonomous system, in which one of the parameters is modulated harmonically. The Duffing oscillator is commonly used as a general example in theoretical of non-autonomous system, whereas the fiber laser is the practical example of such a system. In numerical calculation we used fourth-order Runge-Kutta algorithm. Time series, phase space diagram, and bifurcation diagram has been used to visualize the dynamic behavior of the system."